Control system for uhf rfid passive tags

ABSTRACT

A power control unit is provided to monitor the output power of a charge pump converter having an input impedance and an input impedance controlling terminal to be plugged to the power control unit and modify the input impedance. The power control unit includes a control circuit sense the output power of the charge pump converter and a control unit to receive the sensed power value, establish a control value, and send the control value to the impedance controlling terminal so as to modify the input impedance.

TECHNICAL FIELD

The present invention relates to the field of power control unit and inparticular of a power control unit for UHF RFID passive tags.

STATE OF THE ART

In general, in an RFID communication system, the receiving tag antennais adapted to maximize the received signal at a specific frequency, i.e.the tuning frequency f₀. The adaptation is achieved for a specificantenna and tag input impedance.

In this adapted condition, the received power is maximized, and theMismatch Loss, ML for short, is minimized.

Every time the input frequency signal carrier fc differs from f₀, or thetag or antenna impedances differ from the value needed to achieveadaptation the system suffers a loss in the received power.

In operative conditions, the above disrupting scenario may happen forthe following reasons:

-   -   The input signal frequency can operate at different frequencies        in the UHF RFID band [860-960] MHz;    -   Variations in electronic components values due to process or        temperature may cause variation in the tag input impedance; and,    -   Environmental conditions in which the tag operates, e.g. medium,        humidity, temperature, may alter the antenna adaptation.

Therefore, there is a need to maximize the tag reading distance and thisindependently of the operative conditions.

SUMMARY OF THE INVENTION

In order to achieve this objective, the present invention provides apower control unit configured to monitor the output power of a devicehaving an input impedance between a first input terminal and a secondinput terminal, and having a first output terminal, a second outputterminal and an input impedance controlling terminal configured to beplugged to said power control unit; said input impedance controllingterminal is configured to modify said input impedance; said powercontrol unit comprising at least:

-   -   a control circuit: said at least control circuit is configured        to sense said output power of said device through said first        output terminal and said second output terminal and to transmit        a sensed power value as a function of the sensed output power;        and    -   a control unit: said at least a control unit is configured to        receive said sensed power value, to establish a control value        and to send said control value to said impedance controlling        terminal such as to modify said input impedance.

Thus, this configuration allows sensing the received power and takeactions to minimize the tag sensitivity and thus maximize the tagreading distance.

According to an embodiment, said sensed power value comprises a voltagesensed power value and/or current sensed power value.

According to an embodiment, said voltage sensed power value and/or saidcurrent sensed power value is or are analog signal.

Thus, the transmission of said sensed power value as a function of thesensed output power is quicker than digital signal.

According to an embodiment, said control circuit comprises at least onecontrol circuit configured to determine at least a first physicalquantity between said first terminal and said second terminal and tomeasure at least a second physical quantity.

According to an embodiment, said control circuit is configured tocontrol an output current from said device and to measure an outputvoltage between said first output terminal and said second outputterminal at lower input power levels across said first input terminaland said second input terminal, and/or to control said output voltageand measure said output current at higher input power levels.

According to an embodiment, said at least control circuit is configuredto conduct a current value by diverting said output current from saidfirst output terminal to said second output terminal such as to evaluatethe sensed power value.

According to an embodiment, said at least a control circuit comprises atleast:

-   -   a power input terminal: said power input terminal is configured        to sense said output current and/or said output voltage value of        said device;    -   an internal reference: said at least internal reference is        configured to set a reference value;    -   a comparison circuit: said at least a comparison circuit        configured to compare said reference value to said output        current value and/or said output voltage value; and    -   a current limited buffer: said at least a current limited buffer        is configured to divert the current from said first output        terminal to said second output terminal such as to evaluate the        sensed power value.

According to an embodiment, said at least control unit comprises atleast a controller configured to establish an established voltage valueand/or an established current value as a function of said sensed currentvalue and/or said sensed voltage value of said device.

According to an embodiment, said at least bias supplier comprises atleast a converter configured to convert said sensed current value and/orsaid sensed voltage value of said device into a digital voltage valueand/or a digital current value.

The present invention relates to a control system device comprising atleast one power control unit according any preceding claims and at leastone charge pump converter; said at least one charge pump convertercomprising at least one primary gate controller and at least onesecondary gate controller; said at least one primary gate controllercomprises at least one;

-   -   primary signal output: said at least one primary signal output        is configured to be connected to an at least one second primary        signal input of a charge pump converter and/or a first circuit;    -   first primary signal input: said at least one first primary        signal input is configured to receive a first control signal;    -   primary bias input: said at least one primary bias input        configured to establish a voltage value and/or a current value        of said at least one primary gate controller;    -   second primary signal input: said at least one second primary        signal input configured to be connected to an at least one        primary signal output of a charge pump converter and/or to        receive said main signal, preferably from an antenna, from an        integrated circuit, at least one primary signal and/or from a        charge pump converter; and,    -   said at least one secondary gate controller comprises at least        one:    -   secondary signal output: said at least one secondary signal        output is configured to be connected to an at least one second        secondary signal input of a charge pump converter and/or a        second circuit;    -   first secondary signal input: said at least one first secondary        signal input is configured to receive a second control signal;    -   secondary bias input: at least one secondary bias input        configured to establish a voltage value and/or a current value        of said at least one secondary gate controller; and,    -   second secondary signal input: said at least one second        secondary signal input configured to be connected to an at least        one secondary signal output of a charge pump converter and/or to        receive a main signal, preferably from an antenna, from an        integrated circuit, at least one secondary signal and/or from a        charge pump converter;    -   said at least one first primary signal input is configured to be        connected to said at least one secondary signal output and said        at least one first secondary signal input is configured to be        connected to said at least one primary signal output.

Thanks to the arrangement according to the invention, said controlsystem device allows sensing the received power and take actions tominimize the tag sensitivity and thus maximize the tag reading distanceby adjusting the bias voltage of the gate by coupling the gate of theswitching element to the output of the previous charge pump converterstage and said at least one bias input, which sets the DC gate's voltagereference bias.

According to an embodiment, said at least one primary gate controllercomprises at least one primary switching element having a primaryconduction path with a first primary terminal and a second primaryterminal, and a primary gate configured to control the current flowingthrough said primary conduction path, said primary conduction path beingconfigured to provide said at least one primary signal; said primarygate is configured to be connected to said at least one first primarysignal input and to said at least one primary bias input, and/or whereinsaid at least one secondary gate controller comprises at least onesecondary switching element having a secondary conduction path with afirst secondary terminal and a second secondary terminal, and asecondary gate configured to control the current flowing through saidsecondary conduction path, said secondary conduction path beingconfigured to provide said at least one secondary signal; said secondarygate is configured to be connected to said at least one first secondarysignal input and to said at least one secondary bias input.

Thanks to the arrangement according to the invention, the charge pumpconverter stage allows adjusting the bias voltage of the gate bycoupling the gate of the switching element to the output of the previouscharge pump converter stage and said at least one bias input, which setsthe DC gate's voltage reference bias.

According to an embodiment, said at least one primary bias inputcomprises a plurality of primary bias current flow controller comprisingat least one first primary bias current flow controller and/or at leastone second primary bias transistor and/or wherein said at least onesecondary bias input comprises a plurality of secondary bias currentflow controller comprising at least one first secondary bias currentflow controller and/or at least one second secondary bias transistor.

According to an embodiment, said at least one charge pump convertercomprises at least one input impedance controlling terminal configuredto be plugged to said power control unit such as to modify said inputimpedance.

According to an embodiment, said at least one input impedancecontrolling terminal is configured to control the current flowingthrough said primary conduction path or said secondary conduction pathand preferably of said at least one first primary bias current flowcontroller said at least one second primary bias transistor, said atleast one first secondary bias current flow controller and/or said atleast one second secondary bias transistor.

Thanks to one of those arrangements according to the invention, theconduction path of the switching element may be controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other purposes, features, aspects and advantages ofthe invention will become apparent from the following detaileddescription of the embodiments, given by way of illustration and notlimitation with reference to the accompanying drawings, in which:

FIGS. 1A and 1B represent a control system device 600 according to theinvention;

FIG. 2 shows a block diagram;

FIG. 3 illustrates a parallel equivalent circuit and a series equivalentcircuit of at least one charge pump converter 500;

FIGS. 4A-4G represent a AutoMatch tag performances at f_(in)=f₀;

FIG. 5 represents a AutoMatch tag performances at f_(in)=f₀−55 MHz;

FIG. 6 illustrates a AutoMatch tag performances at f_(in)=f₀+45 MHz;and,

FIG. 7 represents a control system device 600 comprising a plurality ofcharge pump converters 500 and at least one power control unit 100according to the invention.

DESCRIPTION OF THE INVENTION

The present invention relates to a control system device 600 comprisingat least one charge pump converter 500 and at least one power controlunit 100 configured to monitor the output power of said at least onecharge pump converter 500 such as to maximize the received signal at aspecific frequency, i.e. the tuning frequency f₀.

Indeed, said power control unit 100 may be connected to a ProgrammableSelf-Biased Gate Control 500, PSBGC 500 for short.

Said Programmable Self-Biased Gate Control 500 or PSBGC 500 may have aninput impedance between at least one second primary signal input 210 andat least one second secondary signal input 310, and at least one primarysignal output 250, at least one secondary signal output 350 and an inputimpedance controlling terminal 513, as illustrated in FIG. 1 .

Said input impedance controlling terminal 513 may be configured to beplugged to said power control unit 100 and to modify said inputimpedance according a signal from said power control unit 100.

Effectively, to maximize the received power, P_(in) 910 for short, is anecessary but not yet enough condition to maximize the load power, i.e.the rectifier output power, P_(out) 920 for short, and in order tomaximize the load power it is necessary to maximize also the rectifierefficiency, eff 105 for short, see FIG. 2 .

The relation between the power available at the antenna, P_(avail) 930for short, and the load power, P_(out) for short, being:

$P_{out} = {{P_{avail}*\frac{eff}{ML}{where}{eff}} = {{\frac{P_{out}}{P_{in}}{and}{ML}} = \frac{P_{avail}}{P_{in}}}}$

The mismatch loss, ML 905 for short, can be expressed in terms of theseries impedances of antenna and tag as:

$\frac{1}{ML} = \frac{4R_{a}R_{ts}}{\left( {R_{a} + R_{ts}} \right)^{2} + \left( {X_{a} + X_{ts}} \right)^{2}}$

Where the antenna series impedance is Z_(α)=R_(α)+jX_(α) and the tagseries impedance is Z_(ts)=R_(ts)+jX_(ts).

The ML is minimized, i.e. ML=1, at conjugate matching. In others words,when R_(α)=R_(ts) and X_(α)=X_(ts).

The following «match» parameter is used hereafter to quantify the loadpower for a given available power:

$\frac{eff}{ML} = {{{eff}*\frac{4R_{a}R_{ts}}{\left( {R_{a} + R_{ts}} \right)^{2} + \left( {X_{a} + X_{ts}} \right)^{2}}} = {{\frac{P_{out}}{P_{avail}}{with}0} \leq \frac{eff}{ML} \leq 1}}$

In a RFID tag front-end the input equivalent circuit is a parallel of aresistance, R_(tp) 904 for short, and a capacitance, C_(tp) 903 forshort.

The input parallel resistance is defined by the rectifier input parallelresistance.

At the frequency f₀ the parallel equivalent circuit can be representedby the equivalent series circuit, R_(ts) 907 and C_(ts) 906, accordingto the transformation formulas:

$\begin{matrix}{R_{ts} = \frac{R_{tp}}{1 + Q^{2}}} \\{C_{ts} = {C_{tp}\frac{1 + Q^{2}}{Q^{2}}}} \\{Q = {2\pi f_{0}C_{tp}R_{tp}}}\end{matrix}$

Said power control unit 100, according to the present invention, maysense the rectifier output power P_(out) and controls the matchparameter thus in turn controlling the rectifier input resistance R_(tp)and efficiency eff. The match parameter may be a function of ML, i.e.function of R_(ts) and R_(tp), and eff.

The control on the rectifier input resistance and efficiency is based oncharge pump topology, as described in EP19207239, in particular, theapplicant hereby incorporate p.5, I.24-p7, I.30, p.8, I.3-p.9, I.17,p.9, I.20-p.10, I.2 and p.11, I.1-24 by reference to EP19207239.

More precisely, the control on the rectifier input resistance andefficiency may act on a gate controller 200, 300 of a charge pumpconverter 500.

Said charge pump converter 500 may have an input impedance between afirst input terminal 210 and a second input terminal 310, and a firstoutput terminal 250, a second output terminal 350, a primary biascurrent flow controller 225, a secondary bias current flow controller325, a primary attenuator controlling terminal 435 and a secondaryattenuator controlling terminal 445, as illustrated in FIGS. 1A and 1B.

Said primary bias current flow controller 225 and said secondary biascurrent flow controller 325 may be configured to be plugged to saidpower control unit 100 and to modify input impedance, and said primaryattenuator controlling terminal 435 and said secondary attenuatorcontrolling terminal 445 may be configured to be plugged to said powercontrol unit 100 and to modify a K-factor.

Effectively, to maximize the received power, P_(in) 910 for short, maybe a necessary but not yet enough condition to maximize the load power,i.e. the rectifier output power, P_(out) 920 for short, and in order tomaximize the load power it may be necessary to maximize also therectifier efficiency, eff 105 for short, and the K-factor, also known asQ-factor.

The relation between the power available at the antenna, P_(avail) 930for short, and the load power, P_(out) for short, being:

$P_{out} = {{P_{avail}*\frac{eff}{ML}{where}{eff}} = {{\frac{P_{out}}{P_{in}}{and}{ML}} = \frac{P_{avail}}{P_{in}}}}$

The mismatch loss, ML 905 for short, can be expressed in terms of theseries impedances of antenna and tag as:

$\frac{1}{ML} = \frac{4R_{a}R_{ts}}{\left( {R_{a} + R_{ts}} \right)^{2} + \left( {X_{a} + X_{ts}} \right)^{2}}$

Where the antenna series impedance may be Z_(α)=R_(α)+jX_(α) and the tagseries impedance may be Z_(ts)=R_(ts)+R_(ts)+jX_(ts).

The ML may be minimized, i.e. ML=1, at conjugate matching. In otherswords, when R_(α)=R_(ts) and X_(α)=X_(ts).

The following «match» parameter may be used hereafter to quantify theload power for a given available power:

$\frac{eff}{ML} = {{{eff}*\frac{4R_{a}R_{ts}}{\left( {R_{a} + R_{ts}} \right)^{2} + \left( {X_{a} + X_{ts}} \right)^{2}}} = {{\frac{P_{out}}{P_{avail}}{with}0} \leq \frac{eff}{ML} \leq 1}}$

In a RFID tag front-end the input equivalent circuit may be a parallelof a resistance, R_(tp) 904 for short, and a capacitance, C_(tp) 903 forshort.

The input parallel resistance may be defined by the rectifier inputparallel resistance.

At the frequency f₀ the parallel equivalent circuit can be representedby the equivalent series circuit, R_(ts) 907 and C_(ts) 906, accordingto the transformation formulas:

$\begin{matrix}{R_{ts} = \frac{R_{tp}}{1 + Q^{2}}} \\{C_{ts} = {C_{tp}\frac{1 + Q^{2}}{Q^{2}}}} \\{Q = {2\pi f_{0}C_{tp}R_{tp}}}\end{matrix}$

Said power control unit 100, according to the present invention, maysense the rectifier output power P_(out) and controls the matchparameter thus in turn controlling the rectifier input resistance R_(tp)and efficiency eff. The match parameter may be a function of ML, i.e.function of R_(ts) and R_(tp), and eff.

The control on the rectifier input resistance and efficiency may bebased on charge pump converter topology, as described in EP19207239, inparticular, the applicant hereby incorporate p.5, I.24-p7, I.30, p.8,I.3-p.9, I.17, p.9, I.20-p.10, I.2 and p.11, I.1-24 by reference toEP19207239.

More precisely, the control on the rectifier input resistance andefficiency may act on said primary bias current flow controller 225 andsaid secondary bias current flow controller 325, and said primaryattenuator controlling terminal 435 and said secondary attenuatorcontrolling terminal 445 respectively of said charge pump converter 500.

Said charge pump converter 500 may comprise at least one primary gatecontroller 200 and at least one secondary gate controller 300 asdepicted in FIGS. 1A and 1B. Said at least one primary gate controller200 may comprise at least one primary signal output 250, at least onefirst primary signal input 230, at least one primary bias input 220 andat least one second primary signal input 210.

Said at least one primary signal output 250 may be connected to at leastone power control unit 100 or in series to a first circuit and/or an atleast one second primary signal input 210 of a charge pump converter500. Indeed, said at least one second primary signal input 210 may beconnected to, preferably directly connected to an at least one primarysignal output 250 of a following charge pump converter 500 and/or toreceive a main signal, preferably from an antenna, from an integratedcircuit and/or from a charge pump converter 500, and said at least onefirst primary signal input 230 may receive a first control signal andsaid at least one primary bias input 220 may establish a voltage valueand/or a current value of said at least one primary gate controller 200.

Further, said at least one primary gate controller 200 may comprise atleast one primary switching element 240 having a primary conduction path245 with a first primary terminal 241 and a second primary terminal 242,and a primary gate 243 configured to control the current flowing throughsaid primary conduction path 245: said primary conduction path 245 mayprovide said at least one primary signal. By controlling, the skilledman in the art would understand that the current flowing through saidprimary conduction path 245 or said secondary conduction path 345 may bevaried in amplitude, frequency, and/or in phase such as to betransmitted to another charge pump converter for instance as shown inFIG. 1 .

Said primary gate 243 may be also connected to, preferably directlyconnected to said at least one first primary signal input 230 preferablyvia at least one primary coupling capacitor 231 and to said at least oneprimary bias input 220 via at least one primary bias element 221, likeat least one first primary bias current flow controller 221. So, thecharge pump converter allows adjusting the bias voltage of said primarygate 243 by coupling said primary gate 243 of the switching element tothe output of the previous charge pump converter and/or said at leastone bias input, which sets the DC gate's voltage reference bias.

Similarly to said at least one primary gate controller 200, said atleast one secondary gate controller 300 may comprise at least onesecondary signal output 350, at least one first secondary signal input330, at least one secondary bias input 320 and at least one secondsecondary signal input 310. Said secondary gate 343 may be alsoconnected to, preferably directly connected to said at least one firstsecondary signal input 330 preferably via at least one secondarycoupling capacitor 331 and to said at least one secondary bias input 320via at least one secondary bias element 321, like at least one firstsecondary bias current flow controller 321.

Said at least one secondary signal output 350 may be connected to atleast one power control unit 100 or in series to a second circuit an atleast one second secondary signal input 310 of a charge pump converter500. Indeed, said at least one second secondary signal input 310 may beconnected to, preferably directly connected to an at least one secondarysignal output 350 of a following charge pump converter 500 and/or toreceive said main signal, preferably from an antenna, from an integratedcircuit and/or from a charge pump converter 500, and said at least onefirst secondary signal input 330 may receive a second control signal,and said at least one secondary bias input 320 may establish a voltagevalue and/or a current value of said at least one secondary gatecontroller 300. As shown in FIG. 1B, said at least one first primarysignal input 230 may be connected to, preferably directly connected tosaid at least one primary signal output 250 and said at least one firstsecondary signal input 330 may be connected to, preferably directlyconnected to said at least one secondary signal output 350.

Further, said at least one secondary gate controller 300 may comprise atleast one secondary switching element 340 having a secondary conductionpath 345 with a first secondary terminal 341 and a second secondaryterminal 342, and a secondary gate 343 configured to control the currentflowing through said secondary conduction path 345: said secondaryconduction path 345 may provide said at least one secondary signal.

Said secondary gate 343 may be also configured to be connected to,preferably directly connected to said at least one first secondarysignal input 330, via at least one secondary coupling capacitor 331, andto said at least one secondary bias input 320. So, the charge pumpconverter allows adjusting the bias voltage of said secondary gate 343by coupling the said secondary gate 343 of the switching element to theoutput of the previous charge pump converter and said at least one biasinput, which sets the DC gate's voltage reference bias.

In order to adjust the bias voltage of the gates 243, 343, the gates243, 343 of the switching elements in said at least one primary gatecontroller 200 and said at least one secondary gate controller 300 maybe coupled to the output of the previous charge pump converter and/orsaid at least one bias input 220, 320, which sets the DC gate's voltagereference bias. More specifically, the present invention may comprisesaid at least one primary gate controller 200 and said at least onesecondary gate controller 300 having said primary gate 243, said atleast one primary bias input 220 connected to, preferably directlyconnected to said primary gate 243 through a bias element like aresistor or a transistor and said secondary gate 343, said at least onesecondary bias input 320 connected to, preferably directly connected tosaid secondary gate 343 through at least one primary bias element 221and/or at least one secondary bias element 321 like a resistor or atransistor respectively such as to control the DC voltage bias of saidprimary gate 243 and said secondary gate 343 and therefore theconductivity of at least one primary switching element 240 and at leastone secondary switching element 340 respectively. Said bias inputs, moreprecisely said at least one primary bias input 220 and said at least onesecondary bias input 320 may be properly connected to, preferablydirectly connected to internal nodes of said charge pump converter 500such that said at least one primary gate controller 200 and said atleast one secondary gate controller 300 may be self-biased without usingbias-reference external to the charge pump. As it may be in FIG. 1B,where said at least one primary bias input 220 may be directly connectedto, preferably directly connected to said at least one second primarysignal input 210, and said at least one secondary bias input 320 may bedirectly connected to, preferably directly connected to said at leastone second secondary signal input 310.

As previously mentioned, said bias element may be a resistor or atransistor. Indeed, said at least one primary bias input 220 maycomprise at least one first primary bias current flow controller 221,like at least one first primary bias transistor 221. In someembodiments, said primary gate 243 may be connected to, preferablydirectly connected to said second primary terminal 242, rather said atleast one primary signal output 250 via an at least one second primarybias current flow controller 222 and/or at least one second primary biastransistor thus the primary conduction path 245 of the primary switchingelement 240 may be controlled. The same may apply for the secondaryswitching element 340 with at least one first secondary bias currentflow controller 221, like at least one first secondary bias transistor221 and at least one second secondary bias current flow controller 322like at least one second secondary bias transistor.

The applicant does not exclude the gate voltage of said primary gate 243may be determined by configuration of said at least one first primarybias current flow controller 221, like a resistor, and at least onesecond primary bias current flow controller 222, like a resistor,forming a resistive divider and the DC primary gate voltage may becomprised between the voltage value of said at least one second primarysignal input 210 and of a second primary terminal 242. The same mayapply for the secondary switching element 340.

According to some embodiments not represented, instead of a resistor assaid at least one first primary bias current flow controller 221 and/oras said at least one second primary bias current flow controller 222, atransistor and preferably by a MOS transistor may be used such as theprimary conduction path 245 of the primary switching element 240 may becontrolled and may make said charge pump converter 500 programmable andmore specifically said at least one primary gate controller 200programmable. The same may apply for the secondary switching element340.

Further, said at least one first primary bias transistor 221 may betrimmed, via at least one impedance controlling terminal 513, such as tocontrol the current flowing through and/or said at least one firstprimary bias transistor 221 and/or wherein said at least one secondprimary bias transistor may be trimmed, via at least one impedancecontrolling terminal 513, such as to control the current flowing throughsaid at least one first primary bias transistor 221. So, the primaryconduction path 245 of the switching element 240 may be controlled whichmakes the charge pump converter programmable via an integrated circuit,a microcontroller and/or a processor. The same may apply for thesecondary switching element 340.

As shown in FIGS. 1A and 1B, said at least one first primary biastransistor 221 and/or said at least one second primary bias transistor222 may comprise at least one impedance controlling terminal 513configured to trim the current flowing through said at least one firstprimary bias transistor 221 and/or said at least one second primary biastransistor 222 as aforementioned.

Thanks to the arrangements according to the invention, the conductionpath of at least one primary switching element 240 and/or at least onesecondary switching element 340 may be controlled which makes the chargepump converter programmable via said at least one power control unit 100and more particularly via said first input impedance controllingterminal 513.

The same may apply for said at least one first secondary bias transistorand said at least one second secondary bias transistor.

The applicant may want to have a linear control of said charge pumpconverter 500 programmable and more specifically said at least oneprimary gate controller 200 programmable a potentiometer and/or thedigital potentiometer may replace said transistor and preferably saidMOS transistor in linear with a controlled channel resistance. Since theplurality of primary bias transistor and secondary bias transistor maycomprise at least one first primary bias transistor 221 and/or at leastone second primary bias transistor 222, the conduction path 245 of theprimary switching element 240 may be linearly controlled and may makethe charge pump converter programmable via said at least one powercontrol unit 100. The same may apply for the secondary switching element340.

Thus, for a given input power, by maximizing the output power in saidcharge pump converter 500 relatively constant over process andtemperature variations for example, input resistance R_(tp) andrectifier efficiency eff may be obtained.

It follows that said power control unit 100, by reducing the spread ofthe match parameter makes the Sensitivity and the reading distance tagperformance more constant and reliable across temperature and processvariations.

It also follows that said power control unit 100, by reducing the spreadof the rectifier input resistance R_(tp) makes the tag quality factor Qmore constant over temperature and process variations enabling moreconsistent Sensitivity and tag reading distance performances across theUHF band.

At the resonance, i.e. when X_(α)=−X_(ts), it may be possible that theequivalent series resistance at resonance R_(ts) matches the antennaresistance R_(α) minimizing the mismatch loss ML.

If the P_(avail) may be the minimum input power at which the Tag canoperate, then said power control unit 100 may minimize the tagSensitivity and may maximize the tag reading distance over temperatureand process variations.

Thus, using a PSBGC rectifier and said power control unit 100, it may bepossible to perform an automatic control of the input resistance, via atleast one impedance controlling terminal 513, and efficiency of thematch parameter of the PSBGC rectifier.

In order to achieve this objective, said power control unit 100 maycomprise at least one reference circuit 110, and at least one controlunit 120.

More precisely, the control on the rectifier input resistance andefficiency may act on a gate controller of a charge pump converter.

Said charge pump converter comprising at least a switching elementhaving a conduction path with a first terminal and a second terminal,and a gate configured to control the current flowing through saidconduction path, said conduction path being configured to provide asignal. Said gate controller comprising at least a coupling capacitorand at least a signal input configured to be connected to a secondterminal of a charge pump converter and/or to receive a signal,preferably from an antenna, from an integrated circuit and/or from acharge pump converter and to transfer said signal to said first terminalof conduction path of said at least a switching element.

Further, said gate controller of a charge pump converter may comprise atleast a bias input configured to be connected to said gate and toestablish a voltage value and/or a current value of said gate.

Thus, for a given input power, by maximizing the output power in a PSBGCcharge-pump relatively constant over process and temperature variationsfor example, input resistance R_(tp) and rectifier efficiency eff areobtained.

It follows that said power control unit 100, by reducing the spread ofthe match parameter makes the Sensitivity and the reading distance tagperformance more constant and reliable across temperature and processvariations.

It also follows that said power control unit 100, by reducing the spreadof the rectifier input resistance R_(tp) makes the tag quality factor Qmore constant over temperature and process variations enabling moreconsistent Sensitivity and tag reading distance performances across theUHF band.

At the resonance, i.e. when X_(α)=−X_(ts), it may be possible that theequivalent series resistance at resonance R_(ts) matches the antennaresistance R_(α) minimizing the mismatch loss ML.

If the P_(avail) is the minimum input power at which the Tag canoperate, then said power control unit 100 may minimize the tagSensitivity and may maximize the tag reading distance over temperatureand process variations.

Thus, using a PSBGC rectifier and said power control unit 100, it ispossible to perform an automatic control of the input resistance andefficiency of the match parameter of the PSBGC rectifier.

In order to achieve this objective, said power control unit 100comprising at least a control circuit 110, and at least a control unit120.

Said at least control circuit 110 is configured to sense said outputpower of said at least one charge pump converter 500 through said atleast one primary signal output 250 and said at least one secondarysignal output 350 and to transmit a sensed power value 191, which maycomprise a voltage sensed power value and/or current sensed power value,as a function of the sensed output power. According to an embodiment,said voltage sensed power value and/or said current sensed power valuemay be transmitted as analog signal to said at least a control unit 120,which is quicker than digital signal.

Said at least a control unit 120 may be configured to receive saidsensed power value, to establish a control value and to send saidcontrol value to said impedance controlling terminal 513 such as tomodify said input impedance. Thus, said power control unit 100 may sensethe received power and may take actions to minimize the tag sensitivityand thus may maximize the tag reading distance.

As depicted in FIG. 1 , said control circuit 110 may be configured tocontrol an output current from said at least one charge pump converter500 and to measure an output voltage between said at least one primarysignal output 250 and said at least one secondary signal output 350 atlower input power levels across said at least one second primary signalinput 210 and said at least one second secondary signal input 310,and/or to control said output voltage and measure said output current athigher input power levels. Therefore, said control circuit 110 maycomprise at least one control circuit configured to determine at least afirst physical quantity between said at least one second primary signalinput 210 and said at least one second secondary signal input 310 and tomeasure at least a second physical quantity.

In other words, said at least one charge pump converter 500 output poweris sensed with said at least a control circuit 110, which comprises atleast a power input terminal 112 configured to sense said output currentand/or said output voltage value of said at least one charge pumpconverter 500 and at least an internal reference 115 configured to set areference value. During the adaptation of the impedance, said at leastan internal reference 115 may be set such that said output currentand/or said output voltage value of said at least one charge pumpconverter 500 is slightly above the power-on-reset or POR value.

On top of that, at least a comparison circuit 117, comprised in said atleast control circuit 110, is configured to compare said reference valueto said output current value and/or said output voltage value sensed byat least a power input terminal 112.

More specifically, said at least control circuit 110 is configured toconduct a current value by diverting said output current from said atleast one primary signal output 250 to said at least one secondarysignal output 350 such as to evaluate said sensed power value.

Said output current is diverted by at least a current limited buffer 119of said at least a control circuit 110. Said at least a current limitedbuffer 119 is configured to divert the current from said at least oneprimary signal output 250 to said at least one secondary signal output350 such as to evaluate the sensed power value. Indeed, said at least acurrent limited buffer 119 may be a shunt regulator used as controlcircuit, and said diverted current from said at least one primary signaloutput 250 to said at least one secondary signal output 350 or currentshunt may be proportional to said sensed power value.

The analog output of said at least control circuit 110 carries theinformation of said at least one charge pump converter 500 output power,which is converted to a digital word by said at least control unit 120,and more specifically by at least a converter 122. The latter, i.e. saidat least a converter 122, is configured to convert said sensed currentvalue and/or said sensed voltage value of said at least one charge pumpconverter 500 into a digital voltage value 124 and/or a digital currentvalue 124, in other word, a copy of said diverted current 121 isconverted to a digital word 124 by said at least a converter 122.

Said at least control unit 120, previously mentioned, comprises at leasta controller 123 configured to establish an established voltage valueand/or an established current value as a function of said sensed currentvalue and/or said sensed voltage value of said at least one charge pumpconverter 500, such as to find the best trim code to maximize Pout_d.

Thus, thanks to this arrangement, said power control unit 100 may reducethe spread of at least Input Resistance, Mismatch Loss, Quality Factor,Rectifier Efficiency and/or Match parameter over temperature and processvariations.

In addition to the above advantage, if said at least one charge pumpconverter 500, which may be a rectifier, is designed such that the taginput resistance matches the antenna resistance at the minimum inputpower at which the tag can operate, the Tag Sensitivity may be minimizedand/or the Tag reading distance may be maximized over temperature andprocess variations.

FIGS. 4A-4G represent Tag input parallel resistance R_(tp), inputequivalent series resistance R_(ts), Tag mismatch loss ML and TagQuality Factor Q respectively, for a given input power as a function oftemperature and over three process corners for a tag using an 8-stagesdifferential Dickson charge pump with rectifier and with said powercontrol unit 100. In the not trimmed case the trim code to the rectifieris kept fixed. In the trimmed case the trim code to the rectifier isdetermined by said power control unit 100 control loop.

The AutoMatch tag performances are here evaluated for a given inputpower at f_(in)=f₀−55 MHz, see FIG. 5 , with a series resonant RLCantenna-tag equivalent circuit tuned at f₀ and with an antenna qualityfactor equals to 16. In all the plots the performances out of resonanceare compared with the TT-trimmed case at f_(in)=f₀. The «match»parameter is maximized in all the conditions even with an inputfrequency out of resonance X_(α)≠X_(ts).

In FIG. 6 , the AutoMatch tag performances are evaluated for a giveninput power at f_(in)=f₀+45 MHz with a series resonant RLC antenna-tagequivalent circuit tuned at f0 and with an antenna quality factor equalsto 16. In all the plots the performances out of resonance are comparedwith the TT-trimmed case at f_(in)=t₀. The «match» parameter ismaximized in all the conditions even with an input frequency out ofresonance X_(α)≠X_(ts).

1. A power control unit configured to monitor an output power of acharge pump converter having an input impedance between a second primarysignal input and a second secondary signal input, and having a primarysignal output, a secondary signal output, and an input impedancecontrolling terminal configured to be plugged to said power controlunit, said input impedance controlling terminal being configured tomodify said input impedance, said power control unit comprising: acontrol circuit configured to sense said output power of said chargepump converter through said primary signal output and said secondarysignal output, and transmit a sensed power value as a function of thesensed output power; and a control unit configured to receive saidsensed power value, establish a control value, and send said controlvalue to said impedance controlling terminal so as to modify said inputimpedance, wherein the control circuit is further configured to controlan output current from the charge pump converter and measure an outputvoltage between the primary signal output and said secondary signaloutput at lower input power levels across the second primary signalinput and the second secondary signal input, and/or control the outputvoltage and measure the output current at higher input power levels, thecontrol circuit further comprising a power input terminal configured tosense the output current and/or the output voltage value of the chargepump converter, a resistive divider connected to the power inputterminal to be compared in a comparison circuit to an internal referenceconfigured to set a reference value, and a current limited buffer at theoutput of the control circuit linked to the control unit.
 2. The powercontrol unit according to claim 1, wherein said sensed power valuecomprises a voltage sensed power value and/or a current sensed powervalue.
 3. The power control unit according to claim 1, wherein saidcontrol circuit is further configured to determine a first physicalquantity between said second primary signal input and said secondsecondary signal input, and measure at least a second physical quantity.4. (canceled)
 5. The power control unit according to claim 1, whereinsaid control circuit is further configured to conduct a current value bydiverting said output current from said one primary signal output tosaid one secondary signal output so as to evaluate the sensed powervalue.
 6. The power control unit according to claim 1, wherein saidcontrol unit further comprises a controller configured to establish anestablished voltage value and/or an established current value as afunction of said sensed current value and/or said sensed voltage valueof said charge pump converter.
 7. The power control unit according toclaim 1, further comprising a bias supplier including a converterconfigured to convert said sensed current value and/or said sensedvoltage value of said charge pump converter into a digital voltage valueand/or a digital current value.
 8. A control system device comprisingthe power control unit according to claim 1 and the charge pumpconverter, said charge pump converter comprising a primary gatecontroller and a secondary gate controller, said primary gate controllercomprising at least one of: a primary signal output configured to beconnected to a second primary signal input of the charge pump converterand/or a first circuit; a first primary signal input configured toreceive a first control signal; a primary bias input configured toestablish a voltage value and/or a current value of said primary gatecontroller; and a second primary signal input configured to be connectedto the primary signal output of the charge pump converter and/or toreceive said main signal from an integrated circuit, at least oneprimary signal and/or from the charge pump converter; and said at leastone secondary gate controller comprising at least one of: a secondarysignal output configured to be connected to the second secondary signalinput of the charge pump converter and/or a second circuit; a firstsecondary signal input configured to receive a second control signal; asecondary bias input configured to establish a voltage value and/or acurrent value of said secondary gate controller; and a second secondarysignal input configured to be connected to the secondary signal outputof the charge pump converter and/or to receive a main signal from anintegrated circuit, the secondary signal and/or from the charge pumpconverter, said first primary signal input being configured to beconnected to said secondary signal output and said first secondarysignal input being configured to be connected to said primary signaloutput.
 9. The control system device according to claim 8, wherein saidprimary gate controller comprises a primary switching element having aprimary conduction path with a first primary terminal and a secondprimary terminal, and a primary gate configured to control the currentflowing through said primary conduction path, said primary conductionpath being configured to provide said primary signal, wherein saidprimary gate is configured to be connected to said first primary signalinput and to said primary bias input, and/or wherein said at least onesecondary gate controller comprises a secondary switching element havinga secondary conduction path with a first secondary terminal and a secondsecondary terminal, and a secondary gate configured to control thecurrent flowing through said secondary conduction path, said secondaryconduction path being configured to provide said secondary signal, saidsecondary gate being configured to be connected to said first secondarysignal input and to said secondary bias input.
 10. The control systemdevice according to claim 8, wherein said primary bias input comprises aplurality of primary bias current flow controller comprising a firstprimary bias current flow controller and/or a second primary biastransistor and/or wherein said secondary bias input comprises aplurality of secondary bias current flow controllers comprising a firstsecondary bias current flow controller and/or a second secondary biastransistor.
 11. The control system device according to claim 8, whereinsaid charge pump converter comprises the input impedance controllingterminal configured to be plugged to said power control unit so as tomodify said input impedance.
 12. The control system device according toclaim 8, wherein said input impedance controlling terminal is configuredto control the current flowing through said primary conduction path orsaid secondary conduction path and of said first primary bias currentflow controller said second primary bias transistor, said firstsecondary bias current flow controller and/or said second secondary biastransistor.
 13. The power control unit according to claim 1, wherein thecontrol circuit further comprises: a power input terminal configured tosense the output current and/or the output voltage value of said atleast one charge pump converter; an internal reference configured to seta reference value; a comparison circuit configured to compare thereference value to the output current value and/or the output voltagevalue; and a current limited buffer configured to divert the currentfrom the primary signal output to the secondary signal output so as toevaluate the sensed power value.